Development of a Portable Spectroradiometer for Assessing the Light Environment in Crop Production

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

Comments for the Author

In this paper, the authors assessed the feasibility of creating a low-cost portable spectroradiometer for assessing the light environment in crop production. From a reviewer's perspective, this paper is valuable. Nevertheless, the paper still had some issues to solve which need further modification:

--Highlight the importance and significance of this study in Abstract.

--It is recommended to integrate Section 2 “Device design and general characteristics” and Section 4 “Instruments and equipment”. Please provide a system block diagram, which includes modules such as sensors, controller, power management, data storage/transmission, etc.

--Lines 193-195. The literature annotation is incorrect.

--The current conclusion is more like summary of the study. The following components should be included in the conclusion: (1) restating the “thesis”, (2) presenting the key findings of the study, (3) highlighting the broader implications of the study, (4) indicating potential limitations of the study, and (5) suggesting possible lines/areas of future research.

 

Author Response

Reviewer Comments: In this paper, the authors assessed the feasibility of creating a low-cost portable spectroradiometer for assessing the light environment in crop production. From a reviewer's perspective, this paper is valuable.

Response: Thank you very much for taking your time to review this article. Detailed responses are given below, and corresponding corrections are provided in the resubmitted files. All changes in the main text are highlighted in yellow for clarity.

Question 1: Highlight the importance and significance of this study in Abstract.

Response 1: Thank you very much for your kind suggestions. The abstract has been updated, and the significance of the study has been emphasized (Lines 12-13, 24-25).

Question 2:  It is recommended to integrate Section 2 “Device design and general characteristics” and Section 4 “Instruments and equipment”. Please provide a system block diagram, which includes modules such as sensors, controller, power management, data storage/transmission, etc.

Sections 2 and 4 have been integrated into a single Section 2 "Materials and Methods". The block diagram has been added to Figure 2.

Question 3:  Lines 193-195. The literature annotation is incorrect.

The references have been corrected

Question 4:  The current conclusion is more like summary of the study. The following components should be included in the conclusion: (1) restating the “thesis”, (2) presenting the key findings of the study, (3) highlighting the broader implications of the study, (4) indicating potential limitations of the study, and (5) suggesting possible lines/areas of future research.

The Conclusion Section has been revised and expanded (Lines 524-525, 528-541).

Reviewer 2 Report

Comments and Suggestions for Authors

Reviewer comments:

This study conducts the feasibility of creating a low-cost portable spectroradiometer for assessing the light environment in crop production. Besides, it conducts the analysis of the problem and ways to solve it. However, there are some problems for this manuscript.

Detailed comments:
1) Introduction: The introduction is overly simplistic. It is recommended to provide additional explanations regarding the shortcomings of existing light monitoring equipment in terms of portability and spectral resolution, as well as the significance of developing dedicated portable spectral radiometers for the development of precision agriculture. The explanations should be presented in separate paragraphs.

2）Line 67-385: The main headings of the article are too numerous. Should sections “ 2. Device design and general characteristics ” - “ 8. The procedure of PFD calculation based on instrument reading ” be combined into "Materials and Methods" ?

3）Line 194, 195: “ Error! Reference 194 source not found. ” The citation format for references is incorrect.

4）References: The number of references is relatively small. It is recommended to incorporate the supplementary introduction content and increase the number of references.

Comments for author File: Comments.pdf

Author Response

Reviewer Comments: This study conducts the feasibility of creating a low-cost portable spectroradiometer for assessing the light environment in crop production. Besides, it conducts the analysis of the problem and ways to solve it. However, there are some problems for this manuscript.

Response: Thank you very much for taking your time to review this article. Detailed responses are given below, and corresponding corrections are provided in the resubmitted files. All changes in the main text are highlighted in yellow for clarity.

Question 1: Introduction: The introduction is overly simplistic. It is recommended to provide additional explanations regarding the shortcomings of existing light monitoring equipment in terms of portability and spectral resolution, as well as the significance of developing dedicated portable spectral radiometers for the development of precision agriculture. The explanations should be presented in separate paragraphs. 

Response 1: Thank you very much for your kind suggestions. The introduction has been expanded, and references to similar studies have been added. The importance and significance of the study have been emphasized (Lines 48-56, 67-78, 86-88).

Question 2: The main headings of the article are too numerous. Should sections “ 2. Device design and general characteristics ” - “ 8. The procedure of PFD calculation based on instrument reading ” be combined into "Materials and Methods" ?

Response 2: Sections 2 and 4 have been integrated into a single Section 2 "Materials and Methods". Sections 7 and 8 also has been integrated (now it is Section 6).

Question 3: Line 194, 195: “ Error! Reference 194 source not found. ” The citation format for references is incorrect.

Response 3: Thank you, citations and links have been corrected.

Question 4: References: The number of references is relatively small. It is recommended to incorporate the supplementary introduction content and increase the number of references.

Response 5: Thank you for your valuable comments. References to similar studies have been added to the introduction section.

Reviewer 3 Report

Comments and Suggestions for Authors

This manuscript presents an interesting and relevant study on the development of a low-cost portable spectroradiometer for assessing light conditions in crop production, offering potential applications in precision agriculture. The approach combining multi-channel sensors and machine learning is innovative and promising. However, several aspects need improvement before publication, particularly in clarifying methodological details, strengthening the discussion of results, and improving the overall structure and language. In its current form, the work shows potential but requires revisions and corrections to meet publication standards.

Introduction

It would be helpful to split the text into 2–3 paragraphs for easier reading:

1. Importance of light measurement and the technological shift (HPS → LED).
2. Limitations of current methods (lux meters, costly spectrometers, uncalibrated sensors).
3. Justification of the study and objectives.

Rephrase the ending to emphasize the scientific contribution, not just the technical development: “Thus, the purpose of this research is to design and validate a low-cost spectroradiometer for measuring PAR and to develop a processing algorithm capable of accurately reconstructing the spectral distribution of unknown light sources.”
This phrasing strengthens the sense of novelty and scientific relevance.

Materials and methods

2. Device design and general characteristics

The sampling rate, integration time, or data acquisition frequency of the sensors is not indicated.

It is not clear how the two sensors (AS7341 and AS7263) were physically combined e.g., in parallel? using multiplexing? how were overlapping wavelengths handled?

3. Analysis of the problem and ways to solve it

The problem definition could be formulated more precisely  for instance, specify that this is an inverse problem where spectral reconstruction from multi-channel data is underdetermined.

Introduce brief mathematical notation or a general formula to clarify what “spectrum recovery” entails (e.g., linear combination of responsivity functions). This would help readers understand the computational nature of the challenge.

The discussion of “sensor underestimation between responsivity peaks” could be supported with a short example or simulated data illustration (e.g., mention how a 650 nm peak may be misrepresented).

4. Instruments and equipment

The expression “light signals with a narrow intensity band up to 30 nm wide” would be clearer as “light signals with a bandwidth of up to 30 nm.” Likewise, “peak from 400 to 900 nm” should specify whether it refers to the center wavelength or peak emission wavelength.

The authors should include details on measurement uncertainty, repeatability, or the use of radiometric standards or certified filters. This would strengthen the methodological reliability of the work.

The section does not explicitly explain how these measurements contribute to validating the algorithm described earlier. Adding a brief statement that links the calibration process to algorithm validation would improve logical continuity.

7. Determining the light source type

The authors mention that the problem was solved “on small data,” but this is vague. The manuscript should quantify the dataset size and justify why a shallow decision tree was appropriate. Otherwise, it is impossible to assess the robustness or generalizability of the classification model.

The section contains several assumptions about spectral differences among light sources (e.g., ratios of infrared to far-red peaks, lower normalized readings for LEDs). These are theoretically plausible, but the claims should be supported by empirical data or reference spectra either from the authors’ own calibration results or from literature. Adding a figure that shows average spectra or normalized sensor responses for each light source type would strengthen the argument.

Discussion

The authors should highlight how their algorithm outperforms or differs methodologically from previous ones. For instance, it would be valuable to specify whether the current approach improves spectral accuracy, computational efficiency, or generalizability to unknown light sources.

Conclusions

The Conclusions effectively summarize the main achievements, but they could be more concise and focused on the contribution of the study rather than repeating information from the Discussion. Consider separating clearly the main findings, accuracy achieved, and prospective applications into short bullet-style sentences or a paragraph with clearer structure.

Author Response

Reviewer Comments: This manuscript presents an interesting and relevant study on the development of a low-cost portable spectroradiometer for assessing light conditions in crop production, offering potential applications in precision agriculture. The approach combining multi-channel sensors and machine learning is innovative and promising. However, several aspects need improvement before publication, particularly in clarifying methodological details, strengthening the discussion of results, and improving the overall structure and language. In its current form, the work shows potential but requires revisions and corrections to meet publication standards.

Response: Thank you very much for taking your time to review this article. Detailed responses are given below, and corresponding corrections are provided in the resubmitted files. All changes in the main text are highlighted in yellow for clarity.

NOTE: Due to the integration of some sections in response to comments and suggestions in reviews, the section numbers in the responses differ from the section numbers in the comments and correspond to the current structure of the article.

Question 1: Introduction

It would be helpful to split the text into 2–3 paragraphs for easier reading:

1. Importance of light measurement and the technological shift (HPS → LED).
2. Limitations of current methods (lux meters, costly spectrometers, uncalibrated sensors).
3. Justification of the study and objectives.

Rephrase the ending to emphasize the scientific contribution, not just the technical development: “Thus, the purpose of this research is to design and validate a low-cost spectroradiometer for measuring PAR and to develop a processing algorithm capable of accurately reconstructing the spectral distribution of unknown light sources.”
This phrasing strengthens the sense of novelty and scientific relevance.

Response 1: Thank you for your attention to detail in the text and proposal. The introduction has been revised and expanded (Lines 48-56, 67-78, 86-88).

Question 2: Materials and methods

1. Device design and general characteristics

The sampling rate, integration time, or data acquisition frequency of the sensors is not indicated.

It is not clear how the two sensors (AS7341 and AS7263) were physically combined e.g., in parallel? using multiplexing? how were overlapping wavelengths handled?

Response 2: Added information about integration time and connection of devices to the board, lines 115-118. Information about handling of overlapping wavelengths is provided and these decisions are justified in Section 5, lines 344-366.

Question 3: 

1. Analysis of the problem and ways to solve it

The problem definition could be formulated more precisely  for instance, specify that this is an inverse problem where spectral reconstruction from multi-channel data is underdetermined.

Response 3: The formulations have been refined,  lines 149-155.

Question 4: Introduce brief mathematical notation or a general formula to clarify what “spectrum recovery” entails (e.g., linear combination of responsivity functions). This would help readers understand the computational nature of the challenge.

Response 4: Such a notation and formulae were given in Section 5, when discussing the mathematical solution.

Question 5: The discussion of “sensor underestimation between responsivity peaks” could be supported with a short example or simulated data illustration (e.g., mention how a 650 nm peak may be misrepresented).

Response 5: Such an example has been given in Section 7, Figure 13, since it is possible to provide the illustration only after finishing the algorithm.

Question 6: 4 Instruments and equipment

The expression “light signals with a narrow intensity band up to 30 nm wide” would be clearer as “light signals with a bandwidth of up to 30 nm.” Likewise, “peak from 400 to 900 nm” should specify whether it refers to the center wavelength or peak emission wavelength.

Response 6: Corrected, lines 131-133.

Question 7: The authors should include details on measurement uncertainty, repeatability, or the use of radiometric standards or certified filters. This would strengthen the methodological reliability of the work.

Response 7: Information about accuracy and repeatability added, lines 141-145.

Question 8: The section does not explicitly explain how these measurements contribute to validating the algorithm described earlier. Adding a brief statement that links the calibration process to algorithm validation would improve logical continuity.

Response 8: The described calibration process is not for algorithm validation, on the contrary, it precedes the development of an algorithm for which the responsivity values obtained during calibration are used.

Question 9: The authors mention that the problem was solved “on small data,” but this is vague. The manuscript should quantify the dataset size and justify why a shallow decision tree was appropriate. Otherwise, it is impossible to assess the robustness or generalizability of the classification model.

Response 9: Size of data and justification of the algorithm choice added, lines 373-376.

Question 10: The section contains several assumptions about spectral differences among light sources (e.g., ratios of infrared to far-red peaks, lower normalized readings for LEDs). These are theoretically plausible, but the claims should be supported by empirical data or reference spectra either from the authors’ own calibration results or from literature. Adding a figure that shows average spectra or normalized sensor responses for each light source type would strengthen the argument.

Response 10: Figures with HPS and solar spectra and references added to Section 6 (Figure 7, 8).

Question 11: Discussion

The authors should highlight how their algorithm outperforms or differs methodologically from previous ones. For instance, it would be valuable to specify whether the current approach improves spectral accuracy, computational efficiency, or generalizability to unknown light sources.

Response 11: The discussion has been supplemented with information about the distinctive features of the developed algorithm (Lines 511-514).

Question 12: Conclusions

The Conclusions effectively summarize the main achievements, but they could be more concise and focused on the contribution of the study rather than repeating information from the Discussion. Consider separating clearly the main findings, accuracy achieved, and prospective applications into short bullet-style sentences or a paragraph with clearer structure.

Response 12: The Conclusion Section has been revised and expanded. (Lines 524-525, 528-541).

Round 2

Reviewer 3 Report

Comments and Suggestions for Authors

Thank you very much to the authors for the corrections made to the manuscript, which make it sound more scientific and more understandable for readers. In my opinion, the manuscript meets the quality requirements to be published in this journal

Author Response

Thank you very much for your kind suggestions which helped us improve the article